High-speed light-sensitive silver chloride emulsions have not been developed sufficiently, because the intrinsic absorption of the silver chloride emulsion is small, and adsorption of a spectral sensitizing dye onto the silver chloride grains is weak. Consequently, investigation into gold sensitization of a silver chloride emulsion has not been made thoroughly, even though gold sensitization has been applied to a silver bromide- or silver iodobromide-based emulsion, as a matter of course.
However, recently both the demand for high-speed light-sensitive material and the need for realization of more rapid development resulting from compatibility of finely grained silver halide and advances in high speed thereof, are growing. As a prior art relative to gold sensitization concerning the need for such as compatibility of finely grained silver chloride-based silver halide and advances in high speed thereof, there are, for example, JP-A-11-218870 ("JP-A" means unexamined published Japanese patent application), JP-A-11-217388, JP-A-9-118685, JP-A-9-15771, JP-A-9-5922, JP-A-3-151648, JP-A-4-335338, JP-A-6-347944, JP-A-8-62763, Japanese published searched patent publication No. 6-501789, and U.S. Pat. Nos. 5,756,278 and 5,912,112.
However, ionic conductance of the silver chloride-based silver halide emulsion is low, and therefore the supply of silver ions is slow in latent image formation upon exposure to light. Accordingly, the silver chloride-based silver halide emulsion has such an inefficiency that the latent image is considered to hardly grow. It is well known that this defect is particularly related to a property that the so-called high illumination intensity reciprocity law failure is easily caused. On the other hand, it is also well known that gold sensitization is an important technique to solve this problem, since gold sensitization is effective in reducing the minimum size of a latent image that can be developed. However, up to the present time, the effect has been insufficient for the silver chloride-based silver halide emulsion, since the high illumination intensity reciprocity law failure occurs when the kind and amount of a sulfur sensitizer and a gold sensitizer are increased or decreased (mostly, increased) to enhance the sensitivity for a middle illumination intensity exposure to light.
Further, it is also well known that a spectrally sensitized silver chloride-based silver halide emulsion causes a problem of the so-called latent image regression, which means that desensitization occurs, resulting from the latent image being destroyed for a short time after exposure. It is also known that this problem can be overcome by gold sensitization, whereby oxidation-resistance is improved. However, when the kind and amount of a sulfur sensitizer and a gold sensitizer were increased or decreased (mostly, increased) for advances in high speed, the latent image regression still became conspicuous. Consequently, even though various methods were tried, coexistence of improvement in high speed and prevention of latent image regression was difficult to attain sufficiently.